The present invention relates to the field of polyamine analogues having antiproliferative effects.
Polyamines (putrescine, spermidine and spermine) are essential for cell growth, proliferation and DNA synthesis. Depletion of cellular polyamines causes cytotoxicity and death. The polyamine biosynthetic pathway and active support system, under normal conditions, are capable of providing the cell with the required quantity of polyamines for appropriate cell growth and reproduction. Polyamine sources include cell turnover, diet and synthesis by GI flora.
According to the polyamine pathway, putrescine is formed from ornithine by the action of the growth related pyridoxal phosphate-dependent ornithine decarboxylase. Putrescine is converted to spermidine and then to spermine through the consecutive action of two distinct aminopropyltransferases, spermidine synthase and spermine synthase. Both of these enzymes use decarboxylated S-adenosyl-L-methionine (dc-AdoMet) as an aminopropyl donor. The dc-AdoMet is a rate limiting substrate which is formed and controlled by the action of pyruvate-S-adenosyl methionine decarboxylase on S-adenosyl-methionine (AdoMet). Polyamines are interconverted and degraded back to putrescine by the action of two enzymes: cytosolic spermidine/spermidine Nxe2x80x2acetyltransferase, which acetylate the aminopropyl end using acetyl-CoA and polyamine oxidase to split off 3-acetamidopropionaldehyde.
The high polyamine levels in tumor cells can be attributed to the induced activities of the polyamine biosynthetic enzymes. With respect to this observation, specific and potent inhibitors of each enzyme have been synthesized and evaluated for their antitumor activity. The xcex1-difluoromethylornithine (DFMO, Ki=40 xcexcM) is an irreversible inhibitor of ODC. DFMO depletes putricine and spermidine pools, but has little effect on Spermine pools, thereby causing a cytostatic rather than a cytotoxic effect. DFMO has also been used as a chemopreventive agent and to potentiate the antitumor effect of cisplatins and carmustine. The U.S. Food and Drug Administration and the World Health Organization have approved DFMO for treatment of African sleeping sickness cause by T. brudei gambiense. In clinical trials, the more cytostatic putrescine analogue, (2R,5R)-6-heptyne-2,5-diamine (RR-MAP, Ki=3 xcexcm) has been found to cause myclosuppression and renal toxicity. Methylglyoxal-bis-guanylhydrazone (MGBG, Ki less than 1 xcexcM), a model compound, is a strong inhibitor of AdoMetDC. Although it is a well-known anticancer drug, MDG suffers from many disadvantages such as lack of specificity for AdoMetDC. The other potent irreversible inhibitor, 5xe2x80x2-{[(Z)-4-anino-2-butenyl]methylamino}-5xe2x80x2-deoxyadenosin (AbeAdo, Ki=0.3 xcexcM) cures Trypanosoma brucei brucei, (at least 100 times more potent than DFMO) and multi-drug-resistant Trypanosoma brucei rhodesiense infections in mice. S-(5xe2x80x2-deoxy-5xe2x80x2-adenosyl)-1,8-diamino-3-thiooctane (AdoDATO, IC50 less than 50 xcexcM) and S-(-5xe2x80x2-deoxy-5xe2x80x2-adenosyl)-1,12-diamino-3-thio-9-azadodecane (AdoDATAD, IC50=20 xcexcM) are specific multisubstrate adduct inhibitors (transition state complex analogues) of spermidine synthase and spermine synthase, respectively, mainly used in vitro. Complete and selective depletion of PAO by Nxe2x80x2N-bis(2,3-butadienyl)-1,4-butanediamine (MDL 72527, IC50=0.04 mg/kg) did not cause any toxic effect. N-[1-(S-coenzyme A)acetyl]-syn-norspermidine amide (CNSA, IC50=0.3 xcexcM) is a potent multisubstrate inhibitor of SSAT devoid of activity in intact cells due to lack of uptake.
The polyamine transport system is stimulated during proliferation and suppressed during differentiation. This transport is an energy dependent, saturable process for polyamines and synthetic analogues traversing intact the plasma membrane. The polyamine transport may also be viewed as a helpful physiological vector to deliver pharmacologically active substances into the cell.
Several polyamine analogues are known. Antiproliferative agents are seen at table I. Some of the N,Nxe2x80x2-bis ethylated polyamine analogues are effective antiproliferative agents in L1210 murine leukemia cells. Nxe2x80x2,Nxe2x80x3-bis ethylnorspermine (DENSpm, IC50=1.3 xcexcM), Nxe2x80x2,Nxe2x80x3-bis-ethylspermine (DESpm, IC50=0.18 xcexcM) were able to compete with spermine for uptake, accumulate into the cell and deplete all three polyamine pools. These compounds down-regulate ODC and AdoMet-DC in a manner similar to natural exogenous polyamines and induce SSAT. The norspermine analogues were most effective in reducing the polyamine pools in several cell lines. DENSPM is in phase I clinical trial as an antineoplastic.
It is the purpose of this invention to develop a new group tetraamines. May of these novel compounds are chiral compounds which are conformationally restricted polyamine analogues for use in imaging and for therapeutic use in treatment of tumors. These analogues diminish the ability to aggregate DNA seen in the parent polyamines. The invention provides for synthesis of a library of analogues with fine structural modifications which retain restriction and conservation of the molecular weight of the parent polyamines.